Bipolar bioelectrical impedance: lack of accuracy in estimating relative body fat in men

Bioelectrical impedance (BI) is commonly used to estimate body composition in different populations. The aim of this study was to determine the accuracy of bipolar BI (Omron BF 300) in estimating relative body fat (%F) by comparing it with dual-energy X-ray absorptiometry (DEXA). %F was measured in 66 men (18 to 33 years) with a mean body weight of 73.7 plus or minus 8.4 kg, height of 175.1 plus or minus 6.5 cm, body mass index of 23.9 plus or minus 2.2 kg/m super(2), %F sub(BI) 15.1 plus or minus 4.4%, and %F sub(DEXA) 17.7 plus or minus 5.1%. A paired t-test, correlation test, standard error of the estimate (SEE), and residue analysis were used to evaluate the accuracy of the method. BI significantly (p < 0.05) underestimated %F and, the correlation between the two methods was moderate (r = 0.769). Residue analysis showed the lack of agreement between the two methods, with an average error of -2.6 percentage points (95%CI: -9.1; 3.9). The SEE was above the recommended level (>3.5%F) in 42% of the sample. In subjects with higher fat accumulation (%F >20%), the Omron BF BI model produced greater bias in the %F measurement. Therefore, in the case of adult men, the Omron BF 300 BI model does not agree with the DEXA measurement for the estimation of %F in adult men. In addition, the higher the level of fat accumulation, the higher the error in estimated %F.Original Abstract: O objetivo deste estudo foi verificar a acuracidade da IB Bipolar (Omron BF 300) para a estimativa da gordura corporal relativa (G%), comparada com a absortometria de raio X de dupla energia (DXA). A G% foi mensurada em 66 homens (18-33 anos), com massa corporal media de 73,7 plus or minus 8,4 kg; estatura 175,1 plus or minus 6,5 cm; indice de massa corporal 23,9 plus or minus 2,2kg/m super(2); G% sub(IB) 15,1 plus or minus 4,4% e G% sub(DXA) 17,7 plus or minus 5,1%. A acuracidade foi verificada por teste t pareado, correlacao, erro padrao de estimativa (EPE) e analise de residuos. A IB subestimou significati- vamente (p 3,5 G%). Nos individuos com maior acumulo de gordura (G% >20) a IB modelo Omron BF produziu maiores vieses na estimativa da G%. este modelo de IB nao apresentou concordancia com a medida da DXA para estimar a